Thermoplastic resin foam sheets are widely used as sealing materials for filling gaps formed among parts in various products such as imaging equipment including a video movie camera, a digital camera, and a copying machine; electronic devices; mobile phones; housing parts; and automobile parts, with an aim of achieving heat insulation, sound insulation, vibration control, cushioning, watertightness, airtightness and so on.
Various products including mobile phones are now reduced in size and thickness. Along with this trend, the sealing material is used in a very thin state in which the sealing material is compressed in its thickness direction to a thickness of about 0.05 mm. Even in such a state, the sealing material is required to exert excellent sealability.
As such a sealing material, Patent Document 1 discloses a gasket comprising: a substrate consisting of a foam having a hardness of 0.08 to 0.3 kg/cm2 at 25% compression and an elasticity of 0.3 to 0.5 g/cm3; and a plastic film fastened to one surface of the substrate.
However, the gasket has a problem that the flexibility is lowered when compressed to a thickness as thin as about 0.05 mm, resulting in a deteriorated sealability.    Patent Document 1: Japanese Kokai Publication 2001-100216 (JP-A 2001-100216)